The present invention relates more particularly to a method and a device for heating the outside face of a wall of a rotorcraft in order to avoid ice forming and/or accumulating on the said face, and to a rotorcraft wall—in particular a blade of a lift and propulsion rotor—fitted with such a device.
It is well-known that ice forming and accumulating on an outside surface of an aircraft can rapidly modify the aerodynamic characteristics of said surface; in particular when said surface is a rotary wing of a rotorcraft, such icing can cause the rotorcraft to crash.
A large amount of research has been undertaken to prevent or combat the formation of ice.
In U.S. Pat. No. 4,060,212 and FR-2 346 217, proposals are made for a de-icing device using microwaves; in U.S. Pat. No. 4,399,967, U.S. Pat. No. 4,458,865, and U.S. Pat. No. 4,501,398, proposals are made for de-icing the skin of a wing by deforming the skin by using electromagnetic pulses.
Proposals are made for in U.S. Pat. No. 1,819,497 for fitting an airplane wing with a conductor loop that is powered by a high-frequency electric current source in order to induce currents in the metal structure of the wing, heat said structure, and consequently combat icing. The same principle is proposed in U.S. Pat. No. 2,547,934 for de-icing the stator vanes of an air compressor.
Nevertheless, until now, it has not been possible to develop effective induction heating of an aircraft wall, in particular for heating the rotor blades of a rotorcraft; such blades are therefore generally heated by conduction, for example as described in patents US-2005/184193 and FR-2 863 586.
Furthermore, heating an aircraft wall made of composite material comprising reinforcing fibers or fabric embedded in a thermoplastic or thermosetting resin by means of conduction (by the Joule effect), can lead to “hot” points or zones appearing within the wall, and to consequent deterioration of the composite structure.